The Argentine was forced off only 40 minutes into Barcelona’s 1-1 draw with Alavés on Saturday after falling to the floor and holding his chest but was able to walk off the pitch unaided.
Spanish news paper Sport and news agency EFE both subsequently reported Agüero had suffered a heart arrhythmia.
“The first team player Sergio Agüero has been subjected to a diagnostic and therapeutic process by Dr. Josep Brugada,” Barça said in a statement.
“He is unavailable for selection and during the next three months the effectiveness of treatment will be evaluated in order to determine his recovery process.
“The Argentine was taken to hospital for cardiological evaluation on Saturday following the Barça v Alavés game in which the Barça striker felt unwell in the first half and was replaced before half time by Philippe Coutinho.”
“I am doing well and in good spirits to take on the process of recuperation,” Agüero wrote on Twitter. “I want to thank everyone for all their messages of support and love that made my heart stronger today.”
Agüero has struggled with injury since joining the Blaugrana from Manchester City and was only able to make his debut in October.
His absence will only add to Barça’s woes, with the Catalan club recently sacking Ronald Koeman as head coach following an inauspicious start to the season.
Barcelona is languishing in ninth place in La Liga after 11 games, already nine points off league-leader Real Sociedad, and faces a huge clash against Dynamo Kiev in the Champions League on Tuesday.
Interim head coach Sergi Barjuan will be desperate for all three points, as Barcelona sits in third place in Group E behind Bayern Munich and Benfica with just one win from its three matches so far.
Elsewhere, Inter Milan said it will allow Christian Eriksen to move abroad in order to continue his football career.
The Denmark midfielder suffered a cardiac arrest and collapsed during his country’s Euro 2020 match against Finland back in June.
He received life-saving treatment on the pitch and was subsequently fitted with an implantable cardioverter defibrillator (ICD), a small device placed under the skin to monitor heart rate.
It is connected to the heart with thin wires and is able to regulate abnormal heart rhythms through electrical shocks.
However, Eriksen is still unable to play professional football in Italy.
“It should be noted that following a serious injury which occurred during the European Championship in June 2021, the player has been temporarily inhibited by the Italian medical authority from sporting activity in the current season,” Inter said in a statement last week.
“Although the current conditions of the player don’t meet the requirements of achieving sporting fitness in Italy, the same could instead be achieved in other countries where the player could resume competitive activity.”